THE RED SPRUCE. 



55 



be noted. This would ordinarily vary between 25 and 40 per cent, 

 depending on whether maximum solid volume or board-foot volume 

 was the desired object. However, the response to thinnings made 

 in spruce having an average crown length of less than 25 per cent of 

 the height will be exceedingly slow and for that reason of doubtful 

 financial value. 



In Table 19 an attempt is made to predict the yield due to accel- 

 erated growth to be obtained by thinnings made at different ages and 

 with varying degrees of severity. 



Table 19. — Yield from stands of average quality thinned for maximum volume production 

 of pulpwood (unpeeled cords) based on the cutting of dominant {including codominant) 

 and intermediate trees only. Minimum merchantable size, 6 inches in diameter at 

 breastheight and 5 inches in diameter outside bark in the top. 



4 THINNINGS. 



Age of 

 stand. 



Number of dominant and in- 

 termediate trees. 



Propor- 

 tion of 

 trees re- 

 moved. 



Mer- 

 chantable 

 volume 

 of trees 

 removed. 



Final 

 yield. 



Total 

 yield. 



Equiva- 

 lent mean 

 annual 

 growth. 



In fully 

 stocked 



un- 

 th inned 

 stands. 



To be 

 left after 

 thinning. 



To be re- 

 moved in 

 thinning. 



1 



2 



3 



4 



5 



6 



7 



8 



9 



Years. 

 25 

 30 

 35 

 40 



45 



1,316 



1,062 



890 



774 



605 



1,097 

 014 

 762 

 635 



220 

 183 

 152 

 127 



is 



Cords. 



Cords. 



Cords. 



Cords. 



4.9 

 5.6 



7.4 





















44 



61.9 



1.37 



682 



17.9 











3 THINNINGS. 



25 



1,316 

 890 

 697 



605 



1,054 

 791 

 593 



263 



263 

 198 



s 

 i 



4 

 i 











35 



7.1 

 9.5 









45 

 50 









44 



60.6 



1.21 



724 



16.6 











2 THINNINGS. 



30 

 40 



50 



1,062 

 • 774 



605 



849 

 637 



212 

 212 



X 











10.2 









44 



54.2 



1.10 



424 



10.2 











The basic values are taken from Table 17, giving the yields for 

 unthinned, fully stocked, old-field spruce stands of second quality. 

 The volume production of these stands reaches a maximum in the 

 fifty-fifth year and is 44 cords per acre. The assumption is made in 

 Table 19 that 4 thinnings will reduce the natural rotation 10 years; 



